Naturally occurring substances from algae inhibit the development of mosquito larvae. Such substances show signs of acting selectively. The primary objectives of the research are to isolate and identify, such antilarval agents. The project has been initiated with the study of the fresh water green alga Cladophora. Solvent extraction and subsequent chromatography are being employed to isolate the active components. The separation has been monitored by a bioassay using A. triseriatus larvae. Chromatographic and spectral methods are being used for identifications.